1. Field of the Invention
The present invention relates to a highly hydrous soft contact lens which has high water content and good transparency and is able to prevent stain adhesion.
Further the present invention relates to a treating solution for contact lenses, more particularly, to a treating solution contact lenses such as a hard contact lens, an anhydrous soft contact lens and a hydrous soft contact lens to give stain resistance and hydrophilic nature to these lenses.
2. Description of the Prior Art
The highly hydrous soft contact lens is characterized in that it gives little feeling of physical disorder to eyeballs in comparison with a hard contact lens not containing water which essentially comprises a monomer such as methyl methacrylate, and siloxanylalkyl methacrylate (Japanese Patent Publication Sho 52-33502 (1977)). As for a hydrous contact lens, a lens essentially containing 2-hydroxyethyl methacrylate supplies little oxygen and gives feeling of physical disorder to eyeballs. Recently, to increase the percentage of water content, a contact lens comprising a copolymer of N-vinyl-pyrrolidone and methyl methacrylate, 2-hydroxyethyl methacrylate or methacrylic acid was proposed, However, the above contact lens has disadvantage that stains are easily adhered to the lens to lower the strength and the lens grows yellowish by repeated heat treatment for sterilization.
Conventionally used contact lenses may be classified into two groups, anhydrous hard or soft contact lenses and hydrous soft contact lenses.
These anhydrous lenses having advantages over the hydrous lenses in terms of stability of materials and simple care are lenses principally containing methyl-methacrylate or lenses made of silicone rubber. Lately, a hard contact lens having high oxygen permeability principally containing silyl type methacrylate or fluoric type methacrylate which gives moderate effects to eyes has been used.
However, the anhydrous lenses have problems that the hydrophobic surface gives feeling of physical disorder to eyeballs and has bad influence on the cells in the eyeballs. In particular, the lenses having high oxygen permeability and containing silicone or fluorine in large quantities are highly hydrophobic, and there are problems of feeling of physical disorder, lowering of adhesion properties and staining of proteins and lipids. Therefore, to change the hydrophobic surface into a hydrophilic surface, it is known to treat with plasma or chemically treat with acid or basic materials. These methods have problems in the maintenance of the hydrophilic nature, the denaturation after the treatment, and troublesome treating steps. As the other method, for example, there is a method disclosed by Japanese Patent Publication No. 48-37910 (1973) in which a contact lens is immersed into a solution containing a water-soluble polymer of polyvinyl alcohol, hydroxyethyl cellulose, polyvinylpyrrolidone or the like. There are disadvantages that hydrophilic contact lenses are not always obtained by the method and the method is not effective for prevention of stains such as proteins and lipids.
In the other hand, the hydrous soft contact lenses give good fitness to eyes and have no problems. However, these lenses are hydrogel lenses principally constituting 2-hydroxyethyl methacrylate, vinylpyrrolidone or the like, and there are disadvantages of adhesion of proteins, lipids and the like to the lenses, and increase of bacteria for sanitary reasons, and lowered mechanical strength for increased water content. Therefore, sanitary care is commonly required for the lenses by boiling, sterilization or by using a care product such as germicides or detergent liquids.